Process for concentrating organic acids



Patented F ch. 8, 1938 l UNITED STATES PATENT orrlcs amass: PROCESS Foa oolxgl igg'nnmc oncmo Theodore Evans, Oakland, and Karl R. Edlund,

Berkeley, Calif., assi ment Company, San poration of Delaware No Drawing. Application gnors to Shell Francisco, Calif Developa cor- Novcmber 21, 1933,

Serial No.'699,032 38 ((il 260-122) This invention relates to the processes for concentrating various dilute organic acids and is particularly concerned with the methods in which certain solvents are used for this purpose.

A number of processes are known for concensolvent systems from which concentrated acids acid to be concentrated. Upon settling the dilute the acid-solvent layer and the water layer. The acid-solvent phase, containing also some water, is withdrawn and the solvent and water are separated from the acid by distilla- 40 ondary and tertiary ethers, such as methyl 45 methyl secondary isoamyl, ethyl secondary butyl, ethyl secondary amyl, ethyl secondary isoamyl, propyl secondary butyl, propyl secondary amyl, propyl secondary isoamyl, isopropyl secondary butyl, isopropyl secondary amyl, isopropyl sec- ;0 ondary isoamyl, methyl tiary butyl methyl tertiary amyl, ethyl tertiary amyl, and other mixed ethers are excellently suited for use, singly or combined in the above 5 outlined or other organic acid extraction proc- 01' said solvents, without the extraction step. In practice, it is preferable, although not always necessary, to employ solvents having boiling tinuous operation.

; quantities of ethers were the same in all cases. 5

Percent acid Relative Ether used removal efliciency Methyl tertiary butyl 61. 5, 60.0 100. 0 Methyl tertiary amyi. 45. 6 74. 6 Methyl sec. butyl 44. 7 73. 6 Isopropy] 26. 0 42. 8 Diethyl 52. 2, 52. 5 85. 5

Thwe data demonstrate the superiority of mixed ethers over di-isopropyl ether, but the same is not indicated with regard to the diethyl ether.. However, the recovery of concentrated acid requires the step of distilling on the ether, and it is in this stage of the process that the rel- 5 ative deficiency oi diethyl ether is to be noted.

a methyl tertiary butyl ether extract of acetic fully used as components of complex solvents acid can be readily distilled to produce 90% or used for concentrating organic acids. For exbetter acetic acid, ia similar extract of diethyl ample, these ethers can be used together with ether'yieids only 60% acid. other solvents, such as hydrocarbons (pentane, 5;

in carrying out our invention in practice we hexane, light naphthas and the lilge) and/or cer- 5 prefer to employ a continuous process, in which esters, in order to produce solvents afiording a solvent comprising one or more of the mixed higher partition coefficients for the acid and havethers mentioned above is passed through a vering a lower solubility in water, as well as a lower tical contact vessel in an upward iiiow countercapacityto dissolve the same, thus increasing the 3 currently to a stream of a dilute organic acid. efllciency with which a dilute organic acid can be 10 In order to obtain a larger area of contact between concentrated. the aqueous andzsolvent phases we may inject Often, the ilute aliphatic acids which are concur solvent into the contact vessel under more centrated by extraction with suitable solvents or less high pressure through a smalloriflce, or e contain certain quantities of mineral acids. It

accomplish the dispersion of the solvent by some was found, that it is very desirable that these 15 ether physical means. Finely divided glohules of mineral acids were thoroughly removed by neuthe solvent rise then through the descending tralization or precipitation from mixtures either stream of the progressively deconcentrated acid, before or after adding to them or extracting extracting more and more acid as they ascend. them with mixed ethers, because mineral acids On theother hand, if desirable, the solution to promote the decomposition of such ethers par- 20 .be extracted may be dispersed throughout the ticularly at distillation temperatures. However, solvent in a similar manner, the solvent now beif a niiineral acid is left in a mixture to be discoming the continuous phase. tilled, we found, that'by adding an excess oi a As a result of a sumcient contact of the twc known neutralizing agent or precipitant forsuch 2&- phases and due to the solubility characteristics an acid to the distilling mixture, the efiect of acid of the materials used in the process, the acid dis-,- upon mixed ethers is effectively eliminated. For tributes itself according to its partition coefliexample, effective quantitiesc-i BaCoa or Bar-(OH): cient between the water and the solvent phases. or Ba(OOCCH3)z (sjolid or in solution) may be In this manner the acid content of the water used to suppress the eiiect cf the sulfuric acid phase canbe reduced to any desired low value by present in amixture from which a mixed ether is 80 regulating the operating conditions and the relto be removed by distillation; AgOOCCHs may ative quantity of the solvent used in the process. be employed. in the case of hydrochloric acid.

The liquid continuously flowing from the top It is obvious that a large number of the precess of the contact vessel consists essentially of the steps and conditions (temperatures, pressures,

: solvent and the extracted acid, and ountains a. and concentrations) and their combinations can as relatively small quantity of water, which isquite be conceived for concentrating the individual or insoluble in our solvents. mixed dilute organic acidsfin practice by using This acid extract is subjected to a fractional our invention. do not intend, however, to distillation, the acid being produced as the dislimit our laims to any specific method for practillation residue. The vaporized solvent and tising thesam'e, but believe any method or procn steam are condensed into an acid-fr e condeness, either batch or continuous, adapted for conc. being substantially imm Sc b P centrating dilute organic acids and comprising arate into two phases. At ordinary temperatures the step of treating Said acids itr mixed ether the condensed -solvent contains only avery. small in any manner whatsoever, to 3 within the quantity of'water and can be immediately re- Scope of our invention 45 cycled through the process We. claim as our invention:

In certain cases it is possible to accomplish con- L The process for (iohcentmtmg an aqueous centration of a relatively dilute aliphatic acid by simply adding to it a quantity of a mixed ether or a solvent containing such an ether, and then distilling on the solvent and water from the mixture, thereby producing the acid of a higher concentratiori than the original relatively dilute acid. We have'iound that this method of operation serves particularly well when the acid to be concentrated is not very dilute but its concentration is near the cr tical point, i. e. the point when the dilute acid becomes miscible with the selected solvent at a given temperature. I 7 From observations of the processes employ; acetic acid to selective extraction with an agent 6 ing various solvents we have reached a concluesentiauy comprising least. 3 mlxed sion that mixed ethers' are often far superior to alipha e her. the solvents previously used fer concentrating T e pro s fo c cnt f an aqueous organic acids, so that it is possible to produce a carbcxylic acid which comprises subjec n the t5 quantity of the concentrated acetic acid from 9. aqueo s ac to selective extraction w th an agent i 'dilute acid by using far less of a-mixed ether, s a y g p at least one mixed than would be required of diethyl or isopropyl aliphatic tertiary ether. ether, ior example, for producing the same yield ?I' e pr ce s for conc t at an aqllcclls of thegzoncentrated acid. The greater emciency carbcxylic acid which comprises subjecting the 7s of the new process appears to result from the aqueous acid to selective extraction with an agent higher selectivity of the new solvents with reessentially comprising at least one mixed aliphatic gard to the components of an aliphatic acidether possessing a butyl radical linked to the water system. ethereal oxygen atom. We have also discovered that mixed ethers, 6. The process f -r concentratingan aqueous carboxylic acid which comprises subjecting said acid to selective extraction with an agent essen- ;tially comprising at least one mixed aliphatic ether.

2. Theprocess for concentrating anaqueous lower aliphatic carboxylic acid which comprises subjecting said acid tmselective extraction with 'arragent essentially comprising at least one mixed aliphatic ether.

3. The process for concentrating aqueous acetic acid winch comprises subjecting the aqueous such as mentioned hereinbefore, can be successcarboxylic acid which comprises subjecting the essentially comprising acid. 8. The process of claim 7 wherein an aqueous aliphatic acid is treated.-

-.9. The process of claim 7 wherein the solvent employed nially fluid hydrocarbon.

10. In a process for concentrating an organic carboxylic acid 11. The process of claim aliphatic acid is treated.

12. In a continuous 10 wherein an aqueous streams of the solution and a solvent essentially thereby extracting the acid from its aqueous solution, conandsubjecting the rate the concentrated acid from the solvent and to the process.

will er densing the vaporized solvent and Watenthereby producing a non-miscible solvent-water system,

and continuously returning the condensed solvent 14. In a process for concentrating an organic carboxylic acid from its aqueous solution, a step of subjecting said acid solution to a fractional distillation in the presence 01' a solvent essentially trating the acid. 15. In a process for the'recovery of an organic carboxylic acid from its aqueous resultant solution the solvent and water.

16. In a process-for concentrating acetic acid from. its aqueous solution, the steps of extracting the acid from its aqueous solution with a solvent essentially comprising a mixed aliphatic ether and removing the concentrated acid from the extract by tractional distillation. 1'7. Ina process dilute acetic acid, a step comprising subjecting said acid to a fractional distillation in the pres-' ence of a solvent essentially comprising a mixed aliphatic ether, thereby evaporating. the solvent and the water' and concentrating the acid.

18. n a process for concentrating an organic carboxylic acid from its aqueous solution con-i Iorconcentrating a relatively.

taining a mineral acid, the step of subjecting said acid so izing agent insuflicient in amount to substantially neutralize the organic carboxylic acid.

acidis sulphuric acid and the neutralizing agent is a barium compound.

20. In a process for concentrating an organic aliphatic ether.

21. The process for continuously separating water from its solution with acetic acid, in which the dilute acid is extracted with ethyl tertiary acid discharged in a concentrated condition from the column base.

22. The

which the ether removes the water in an azeotropic distillation and the formic acid discharged in a concentrated condition from the column base.

23..In' the process of lutionsof one or more of the lower fatty acids, the use of mixed ethers haying normal boiling points between 80 C. and 105 C. for extracting the acid or acids from the water.

24. The process 01" dehydrating aqueous solu- I tions of one or more of the lower fatty acids by distillation in the presence of a mixed'ether having a normal boiling point between 80 C. and 105 C., said ether acting as a withdrawing-agent forthe water.

25. The process for continuously solution with one or separating the aqueous layer discharged after complete exhaustion, the ether layer, containing in an azeotropic distillation and the lower fatty so as to giveconcentrated dehydrating aqu'eouss'o I process substantially complete extracting the acetic acid from the water.

28. Theproce'ss oi dehydrating aqueous acetic acid by distillation in the presence of a mixed ether having a normal boiling point and 105 C., said ether acting as a withdrawing agent for the water.

29. The process for continuously separating water from its solution with acetic acid, in which the dilute acid is extracted with a mixed etherhaving a normal boiling point between 80 and 105 C., the aqueous layer discharged after substantially complete exhaustion, the ether layer, containing substantially all of the acid originally present and part of the water, passed to a column still in which the ether removes the water in an azeotropic distillation'and the acetic acid discharged in a concentrated condition from the column base.

30. The process for separating water? from acetic acid by distillation with a mixed ether having a boiling point between 80 and 105 0., in which the water and ether forms an azeotropic mixture in the still head, the vaporous azeotropic mixture condensed, the condensate separated into a water and an ether layer, the water layer discharged, the ether layer returned to the still head to remove more water, and the process conducted so as to give concentrated acetic acidin the stillipot.

31. The process for separating water from actic acid by distillation with ethyl tertiary amyl ether, in which the water and ether forms an azeotropi'c mixture in the still head, the vaporous azeotropic mixture condensed, the condensate separated into a water and an ether layer, the water layer discharged, the ether layer returned to the still head .to remove more water, and the conducted so as to give concentrated acetic acid in the still pot.

32. The process for continuously separating water from its solution with formic acid, in dilute acid is extracted with a mixed ether having a normal boiling point between 80 and 105 C the aqueous layer discharged after the ether layer, containing substantially all or originally present and part of the water, passed to a column still in'which the'ether removes the water in an azeotropic distillation and the formic acid discharged in a concentrated condition from the column base.

33. The process for separating water from formic acid by distillation with a mixed ether 3 having a boiling point between 80 and 105'C.,

' in which the water and ether forms an azeotropic the vaporous 'azeotropic mixture condensed, the condensate separated into a water and an ether layer, charged, the ether layer returned to the still head to remove more water, and the process conducted so as to give concen formic acid in the still pot.

between 80 the acid the ether layer return the water layer dis-v mal boiling points between 80 and 105 C. for

34. The process for separating water from formic acid by distillation with methyl tertiary amyl ether in which the water and ether forms an azeotropic mixture in the still head, the vaporous azeotropic mixture condensed, the condensate separated into a water and an ether layer, the water layer discharged, the ether layer returned to the still head to remove more water, and the process conducted so as to give concentrated formic acid in the still pot.

35. The process for continuously separating water from its solution with butyric acid, in which the dilute acid is extracted with-a mixed ether having a normal boiling point between 80 and 105 C., the aqueous layer discharged after substantially complete exhaustion, the ether layer, containing substantially all oi the acid originally present and part of the water,'passed to a column still in which the ether removes the water in an azeotropic distillation and the butyric acid discharged in a concentrated condition from the column base. v

36. The process for separating water irom butyric acid by distillation with a mixed ether having a boiling point between 80 and 105 0.," in which the water and ether forms an azeotropic mixture in the still head, the vaporous azeotropic mixture condensed, the condensate separated into a water and an ether layer, the water layer discharged, the ether layer returned to the still head to remove more water, and the process conducted so as to give concentrated butyric acid in the still pot. s

37. The process for continuously separating a substantial amount of the water present in its solution'with one or more of the lower fatty acids from said acid or acids, in which the dilute acid or acids is extracted with a'mixed ether having a C.,. the aqueous layer complete exhaustion, substantially all of present still in which the ether removes part but not all or the water in an azeotropic distillation, and the lower fatty acid or acids are discharged containing some or the water originally present.

38. The process for separating a substantial amount of the water in ,a mixture with one or more or the lower fatty acids by distillation with a mixed ether having a normal boiling point between 80 and 105 0., in which the water and other forms an azeotropicmixture in the still head, the vaporous azeotropic mixture is condensed, the condensate separated into a water and an other layer, the water layer discharged,

to the still head to remove more water, and the process conducted'so as to give fatty acid or acids still containing some water.

the ether layer, I the acid or acids originally THEODORE EVANS. KARL' a. EDLUND.

and part of the water passed to a column I 

